1. Field of the Invention
The present invention relates generally to combustion apparatus and to a method for operating combustion apparatus, and more particularly relates to method and apparatus for the efficient reduction of solid waste material deposited within an enclosure including means for effecting substantially complete thermal combustion of the solid waste material.
2. Description of the Prior Art
The disposal of solid waste is becoming an increasingly serious problem because of the large volumes of municipal and industrial solid waste materials being generated. This material includes a large volume of combustible refuse and a relatively smaller volume of recoverable resources such as ferrous and nonferrous metals. In the case of combustible solid waste products, incineration has proven to be a convenient way of reducing the volume of these products. Incineration units can be installed at industrial plants, apartment complexes, and shopping centers for thermal reduction. Combustion of waste products is a convenient solution in that large volumes of solid waste material can be reduced into a relatively small amount of residue. Therefore transportation and handling of the large quantities of solid waste is minimized to the disposal of the relatively small amount of ash and other residue at a suitable location. Landfills, which often consume large valuable tracts of urban land and which are expensive to maintain as well as being unsanitary and unsightly, can be eliminated or at least utilized more efficiently.
Rapidly escalating energy costs and increased awareness as to the scarcity of fossil fuels has caused many industries and utilities to consider the thermal conversion of solid waste material as an alternate energy source. Concurrently, many municipalities are faced with environmental regulations and community objections which are increasing the cost and problems associated with the operation of conventional solid waste disposal systems. The incineration of waste materials presents formidable problems because of the increasing emphasis on environmental quality which has led to surveillance and regulation by Federal and local authority. Federal and local legislation in this area no longer permit uncontrolled emissions from solid waste incinerators. Clean air legislation regulates the acceptable amount of particulate material and the constituency of off-gases from the waste disposal systems. Failure to abide by the regulatory acts in this area can result in penalties as well as the imposition of permanent injunctions against operation.
Energy and resource recovery from the conversion of municipal solid waste material is now feasible on the relatively small scale afforded by on-site operations due to recent advances in technology. The fuel fraction of municipal waste, refuse derived fuel, can be incinerated in modular combustors and the heat from combustion used to generate steam for process industries, for driving turbine generators, and other applications. The resource fraction of the municipal solid waste, such as ferrous and nonferrous metals, can be extracted during preparation of the refuse derived fuel and sold to secondary metal markets. The remaining fraction or residue of the conversion process can be used for landfill purposes.
Because of the diminishing availability of landfill space within a reasonable distance of metropolitan and industrial areas, and because of the substantial economic benefit derived from the recovery of heat energy and other resources incidental to the thermal conversion of solid waste material, there exists an urgent need for a solid waste disposal system which can operate economically within the boundary of a standard metropolitan statistical area and in compliance with environmental regulations. To date, no system attempting to accomplish these purposes has been entirely satisfactory.
According to conventional prior art approaches, solid waste material is incinerated and heat energy is recovered from the exhaust gases for the generation of steam. For such an operation to be successful, the steam is delivered continuously to an industrial user on a take-or-pay contract basis. The continuous production of steam requires that an adequate supply of refuse derived fuel be made available for incineration on a continuous basis. However, municipal sanitary waste material is typically gathered during a relatively few days of the week. Therefore, a practical energy and resource recovery system must include a primary storage area for accumulating a relatively large supply of municipal solid waste. Additionally, in order to enhance the profitability of the waste recovery operation, the system should include processing equipment for separating and recovering ferrous and nonferrous metals from the combustible waste material for sale to secondary metal markets. Such processing equipment may operate only eight hours a day for five days a week. Therefore, the system should include a secondary storage area for accumulating a relatively large supply of refuse derived fuel which will ensure the continuous operation of one or more incinerators.
The accumulation of such large amounts of solid waste material and refuse derived fuel which are essential to continuous, profitable operation of the incinerators and waste heat recovery system gives rise to large volumes of offensive odors and malodorous gases which must be prevented from escaping into the atmosphere in order to make the presence of such a facility acceptable to the community and in order to comply with environmental regulations.